1. Field of the Invention
The present invention relates to a film peeling method for peeling a film and, for example, to a film peeling method for peeling a surface-protective film which is stuck on a front surface of a wafer. The present invention also relates to a film peeling device for executing this film peeling method.
2. Description of the Related Art
In a semiconductor manufacturing process, there is a tendency that the wafer is made larger in size and thinner in thickness from the viewpoint of enhancing the packing density of the wafer. In order to make the wafer thinner, back-grinding (grinding a back surface) is conducted in which a surface-protective film is stuck on a front surface of the wafer, on which the semiconductor element has been formed, and a back surface of the wafer is ground under the condition that the front surface of this wafer is sucked onto a suction table.
When the wafer is subjected to this back-grinding process, for example, the thickness of the wafer is reduced to 50 micrometers. Therefore, the mechanical strength of the wafer, which has already been subjected to the back-grinding process, is lowered according to the reduction of the thickness. It is necessary that the above surface-protective film is peeled off from the front surface of the wafer after the completion of the back-grinding process. According to the prior art, the surface-protective film is peeled off in such a manner that a peeling tape is stuck on the surface-protective film of the wafer and then the peeling tape is wound up together with the surface-protective film so as to peel off the surface-protective film. However, this method has a problem that the wafer is damaged at the point of time when the peeling tape is stuck onto the surface-protective film because the mechanical strength of the wafer has been greatly lowered.
In order to solve the above problem, Japanese Examined Patent Publication No. 6-91153 discloses the following surface-protective film peeling method. That is, the peeling tape is made to come into pressure contact with a rear end portion of the surface-protective film of the wafer by a sticking roller and, then, the sticking roller is raised and moved forward. Next, the peeling unit is moved from the rear side to the front side so that the surface-protective film can be peeled off from the wafer together with the peeling tape. In this case, the adhesive strength between the peeling tape and the surface-protective film is enhanced at the position where the peeling tape and the surface-protective film are made to come into pressure contact with each other. Therefore, when the peeling unit is moved, it is possible to continuously peel off the surface-protective film in such a manner that the position where the peeling tape and the surface-protective film are made to come into pressure contact with each other is made to be a start point of peeling.
However, as the sticking roller used for the film peeling device described in the Japanese Examined Patent Publication No. 6-91153 is relatively long, in the case where the rear end portion of the wafer is made to come into pressure contact by the sticking roller, a load is given by the sticking roller to a portion of the wafer where peeling tape does not exist. As described before, the thickness of the wafer supplied to the film peeling device is made smaller by back-grinding. Accordingly, there is a possibility that the wafer is damaged at a position where peeling tape does not exist.
In order to easily peel the surface-protective film, it is actually unnecessary to conduct the pressure-contact-operation by the sticking roller even in the portion where peeling tape does not exist. In this case, the entire film peeling device may be made larger in size.
Further, as the sticking roller is moved with the peeling tape, in the case where the film peeling device is used over a long period of time, the sticking roller is polluted with the adhesive of the peeling tape. Accordingly, there is a possibility that the adhesive is transferred onto the suction table. Especially in the case where the thickness of the wafer is reduced by the back-grinding, a distance between the upper face of the wafer and the upper face of the table is small. Therefore, the transfer of the adhesive described above tends to occur. As a porous ceramic plate has been recently used as the suction table in many cases, holes on the sucking plate are clogged by the transfer of the adhesive described above so that the wafer can not be appropriately sucked onto the suction table. In this case, as the adhesive strength of the surface-protective film with respect to the wafer is higher than the sucking force of the table, and the wafer is removed from the suction table together with the peeling tape when moving the peeling unit, this may damage the wafer.
The present invention has been accomplished in view of the above circumstances. It is an object of the present invention to provide a film peeling method capable of peeling a film from a wafer without damaging the wafer and without making the entire device larger in size. It is also an object of the present invention to provide a film peeling device for executing this film peeling method.